Kitchen Island Sink Plumbing

Vent plumbing inside of the cabinet
Vent plumbing inside of the cabinet
Top of Vent Loop
Top of Vent Loop

An Island sink is indispensable when remodeling your kitchen. It gives two people a place to work, without bumping into each other. It also gives the kids a sink to wash up, or rinse something off, while you are preparing food at another sink.

One of the big issues when adding an island sink, is how to vent the waste line. If you have a wall behind the cabinet, the plumbing is no problem, but in an island, most of the time the cabinet is freestanding with an applied finished back. Which is the case here. Other issues can be the joist placement in the floor. This cabinet sat over an electrical chase in the adjoining joist space, so the plumbing had to come up right in the middle of the cabinet. (Less than Ideal!)

The waste and vent line were stubbed up through the toe kick and floor of the cabinet just far enough to accommodate 45 degree fittings that offset the lines over to the edge of the cabinet. The vent loop - [second picture] - should be as tall possible, beside the sink and up to the counter top. The vent loops and goes back down under the floor. The vent line has a T fitting installed that ties into a waste line to drain any condensation or water that gets trapped in the vent line; from the T fitting the vent line runs to the nearest wall and up from there into the attic and through the roof.

Always install a T fitting after the vent line goes back into the floor, otherwise the vent will slowly fill with water and become ineffective over time. There is nothing worse than a slow draining, gurgling, burping sink that vents through the sink drain.

There are after-market mechanical vents available, and these are code approved for mobile homes and repair work, but for this application in a remodel, they really should not be considered. A mechanical vent works with a very weak spring, which holds a rubber diaphragm closed. When draining water runs down from the sink, it creates a suction that pulls on the diaphragm and depresses the spring. These vents work great as long as they are not blocked or obstructed, but spiders build webs. Condensation is corrosive and over time causes mineral buildup, and people throw all kinds of stuff under a sink, so a vent is important and worth doing right.

A little trick to remember when assembling ABS fittings and pipe; make your cuts with a chop saw - wherever they will be visible and wipe off the excess glue with a rag, while assembling the loop. It will be much more attractive and uniform when completed.

More by this Author


Comments 2 comments

Carlos Ramos 6 years ago

Just what I was looking for. Pictures say it all!! Thnx


ConstructionHero profile image

ConstructionHero 6 years ago from Washington Author

I'm glad you guys found this information helpful. Remember the loop vent must be tied to drain line as well as your vent that goes through the roof. If you do not tie it with a T fitting to the drain, it will gradually fill with rain water and condensation, until the vent no longer works.

    Sign in or sign up and post using a HubPages Network account.

    0 of 8192 characters used
    Post Comment

    No HTML is allowed in comments, but URLs will be hyperlinked. Comments are not for promoting your articles or other sites.


    Click to Rate This Article
    working